1. Field of the Invention
The present invention relates to a loudspeaker component and a resin composition used for making such a component. More particularly, the present invention relates to improvements of a loudspeaker component with respect to acoustic properties (i.e., internal loss, elasticity and stiffness), dimensional stability against heat and moisture, and weight.
2. Description of the Related Art
Conventionally, paper has been widely used for making a loudspeaker component such as a diaphragm, a voice coil bobbin, a center cap, a frame, a speaker cabinet or the like. This is because the loudspeaker component made of paper has a light weight while being appropriate with respect to internal loss and stiffness. However, the paper loudspeaker component has been found to be insufficient in water- and moisture-resistance. Further, due to the low elasticity of paper, the paper loudspeaker component fails to provide satisfactory acoustic properties. In addition, since the paper loudspeaker component requires a paper-forming step and a complicated shaping step for its fabrication, the production efficiency is relatively low, but yet the product quality tends to vary from product to product.
On the other hand, proposal has been also made to use a metal foil for making a loudspeaker component. Compared with a paper loudspeaker component, the metal foil loudspeaker component provides improvements with respect water-resistance, moisture-resistance and elastic modulus. However, due to the higher weight of a metal foil, a voice coil bobbin made of a metal foil for example is low in operating efficiency and unsatisfactory with respect to transient characteristics. Further, the metal foil loudspeaker component has a low internal loss, resulting in poor acoustic properties.
In order to solve the above-mentioned problems, research has been made for an engineering plastic material such as polyimide (PI) or polyphenylene sulfide (PPS) as a candidate for making a loudspeaker component having a high elasticity and a light weight. However, due to a large thermal expansion coefficient, a loudspeaker component made of such an engineering plastic material may differ greatly in thermal expansion from another component made of a different material. As a result, these components may be deformed (e.g., from a circular shape to an oval shape) at the connection therebetween, or the connection may be broken (e.g., separation of a voice coil from a voice coil bobbin). In this way, a loudspeaker component made of an engineering plastic material is dimensionally unstable under heat.